Using nitride-based III-V group compound semiconductors such as gallium nitride (GaN), there have been developed semiconductor light emitting devices such as high-intensity ultraviolet to blue and green light emitting diodes (LED) and blue-violet to blue and green laser diodes (LD).
In order to achieve a higher efficiency in an LED, it is important to improve crystallinity of a GaN-based semiconductor, to reduce defects and non-radiative recombination centers, and to increase an internal quantum efficiency inside a crystal. It is also important how to recombine electrons and holes for light emission in an active layer. Electrons are likely to overflow from the active layer. On the other hand, holes are likely to have a low carrier density because an activation ratio of a p-type impurity is low.
JP-B 3446660 proposes the configuration provided with a cap layer between an active layer and a p-type clad layer, the cap layer including a layer which is grown using an N2 gas for preventing the active layer from being separated and a layer which is grown using an H2 gas for forming a potential barrier.
However, this technique still has room for improving a light emitting efficiency.